Enhancement of Electrical Properties on ZnO: Al Thin Film due to Hydrogen Annealing and SiO2Coating in Damp-heat Environment

Abstract

The electrical stability of ZnO: Al thin films deposited on glass substrate by the RF magnetron sputtering method have been modified by a hydrogen annealing treatment and <TEX>$SiO_2$</TEX> protection layer. AZO thin films were deposited at room temperature and different RF powers of 50, 100, 150, and 200 W to optimize the AZO film growth condition. The lowest value of resistivity of <TEX>$9.44{\times}10^{-4}{\Omega}cm$</TEX> was obtained at 2 mtorr, room temperature, and a power level of 150 W. Then, the AZO thin films were annealed at <TEX>$250-400^{\circ}C$</TEX> for 1 h in hydrogen ambient. The minimum resistivity obtained was <TEX>$8.32{\times}10^{-4}{\Omega}cm$</TEX> as-annealed at <TEX>$300^{\circ}C$</TEX>. The electrical properties were enhanced by the hydrogen annealing treatment. After a 72 h damp-heat treatment in harsh conditions of a water steam at <TEX>$110^{\circ}C$</TEX> for four representative samples, a degradation of electrical properties was observed. The sample of hydrogen-annealed AZO thin films with <TEX>$SiO_2$</TEX> protection layer showed a slight degradation ratio(17%) of electrical properties and a preferable transmittance of 90%. The electrical stability of AZO thin films had been modified by hydrogen annealing treatment and <TEX>$SiO_2$</TEX> protection layer.